Although many empirical and theoretical reports indicate that Alcohol Use Disorders (AUDs) involve diverse pathways, few studies have characterized the variability of the long-term nature of the disorder;nor have studies documented adequately the particular influences that account for transitions between problem drinking, non-problem drinking and abstinence. Furthermore, the absence of such longitudinal data is particularly striking for samples of alcoholics beyond the third decade of life, notwithstanding the large number of alcoholics who seek (or continue to receive or return to) treatment well into their midlife. In this application, we focus on (1) the course of alcoholism from onset of problem drinking to midlife with special emphasis on the 40-60 year age period, (2) the identification of individual, interpersonal and contextual influences predictive of long term drinking trajectories and of transitions between problem drinking, non-problem drinking and abstinence, (3) the examination of purportedly environmental influences on drinking transitions within a genetically-informative discordant twin analysis, and (4) the assessment of the generalizability of emergent findings to non-twin samples of treatment and non-treatment seeking alcoholics. Data for the proposed study will be drawn from the Vietnam Era Twin Registry (VETR) which is well suited for our research goals given: (1) the availability of extensive information (from our previous studies of this data base as well as the work of other VETR investigators) on the substance use, psychiatric, demographic, and treatment histories of a large sample of middle age males with lifetime diagnoses of AUD and (2) the VETR comes from a general population sample of male twins rather than from medical or psychiatric treatment seeking sources. Finally, our research team is highly qualified to conduct such research given the considerable experience we have developed in work with large data sets, genetically informative designs, and complex data analytic strategies. Relevance This study's focus on the course of alcoholism over the life course is of particular importance in developing more effective strategies for treating alcohol use disorders and reducing their severity and persistence. The implications of this work are especially relevant to clinical care facilities that must treat large numbers of midlife individuals with alcoholism and related disorders. Clearly, our ability to predict and differentiate such patients in terms of different life course patterns and to identify individual, environmental and contextual variables linked with transitions between problem use, non-problem use and abstinence would be of great importance in patient management and development of more tailored interventions.